This invention relates to vehicle control systems, more specifically to control systems for automobiles or other vehicles employing pneumatic tires.
Advances in technology have enabled vehicles to incorporate computer-controlled features into the operation of the vehicle. Most notably, these features were implemented early on in aircraft and in that technical field the use of xe2x80x9cfly by wire systemsxe2x80x9d or computer-augmented manual control systems has advanced to a fully integrated vertical flight path and speed control system as described in U.S. Pat. No. 4,536,843. The Total Energy Control System (hereinafter referred to as TECS or TEC system) develops fundamental solutions to the problem of coordinated elevator and throttle control to produce performance levels exceeding those generally known in the flight control systems art and is described in U.S. Pat. No. 6,062,513.
Embedded within the TECS are sub systems controlled by TECS including a variety of computer controlled flight systems. Many of these systems automatically react to flight parameters and in various situations these systems sense equipment breakdowns and prevent the pilot from directing the controls in a way that could inadvertently cause a loss of control of the aircraft.
In several aircraft, the reaction of a pilot to equipment failure may overcorrect causing the situation to worsen. The use of computers that have pre-programmed responses to equipment failures insures that the response to a situation is quick and accurate and has been carefully analyzed in test lab conditions to insure a reliable and quick response. The best-experienced pilot may take precious seconds to isolate a problem manually and then he must select from a variety of options and choose the best course of action under a stressful situation.
Historically, airplanes had large amounts of time and usually sufficient airspace and altitude to allow pilots to make optimal choices. Nevertheless, in today""s crowded airspace the use of computers to assist the pilots has been widely adapted.
In automobiles, we are just beginning to see applications of computer-controlled systems and equipment-controlled components. Anti-lock brakes, load-leveling suspensions, cruise control and traction control devices are commonly available.
Some car manufacturers are evaluating and testing computer controlled driverless systems. Advertisements show a string of driverless vehicles traveling at highway speeds on a California expressway. While this advanced technology is currently being tested, it is going to be years before fully automatic driverless vehicles are commercially or socially accepted.
Most importantly, the driver in the near term must be able to act and make good choices. Unlike pilots, driver training in simulated adverse conditions is almost non-existent. Driver error due to fatigue, inexperience or bad judgment is the leading cause of accidents.
In U.S. Pat. No. 6,263,282, issued July 2001, a System and Method for Warning of Dangerous Driving Conditions is disclosed. That patent warns a driver when he is closing too fast on a vehicle such that a reduction in speed or a veering or turn is required. This patent basically gives the driver a xe2x80x9cheads upxe2x80x9d or signal that he should be careful. The driver initiates all action.
In U.S. Pat. No. 6,282,498, a Traveling Direction Correction Apparatus is disclosed. This patent is particularly useful if the driver dozes into a sleep mode and starts to drift out of it""s driving lane. This device enable or activates a brake steering sequence to try to keep the car on the pavement while also sounding an alarm to regain the drivers attention. Falling asleep or driver fatigue behind the wheel of an automobile is one of the leading causes of accidents.
In each of the above referenced patents the attempt is to avoid a driver error before the onset of an accident.
Another opportunity for driver error occurs at the initiation of a flat tire. At one time or another most drivers will experience a flat tire while driving. This problem is basically an inconvenience for most drivers in most situations. Other times, particularly at high speed, a sudden loss of pressure in a tire can be very problematic. If the driver reacts quickly by slamming on the brakes, he can lose control or be run into by following or trailing vehicles. If the driver quickly swerves or turns the steering wheel to maneuver to the side of the road he can easily oversteer the vehicle causing a loss of control. Generally the best advice is to hold steady and allow the vehicle to slow by simply removing the foot from the accelerator or by disengaging the cruise control.
After the vehicle has slowed the application of brakes or steering has a less dramatic affect.
While this seems obvious that every driver should understand this simple concept, it is more apparent that the driver often times reacts quicker than he thinks and therefore simply makes a bad situation worse.
Drivers from areas having icy or snowy conditions learn that loss of traction is not corrected by slamming on brakes. Vehicle control is your first objective in such conditions and slowing down is achieved by a deceleration based on removing the foot from the gas pedal. These common sense rules are easy for those who have practiced driving in these conditions. Drivers in warm climates simply do not have as much opportunity to learn these aspects of driving and therefore snowy or slick driving conditions, usually results in higher accident rates when they occur in the warmer climates.
When a tire experiences a flat or a more rapid rate of pressure loss due to a gash, the vehicle suddenly changes in several ways. The load balance on the vehicle shifts as the flattened tire deflates causing the center of mass to actually shift toward the flattened tire. If the brakes are applied the three inflated tires provide the contact patches that try to stop the vehicle. The deflated tire simply cannot apply an equal braking force to the ground compared to the remaining inflated tire. If the rear tire is flat, braking causes the front of the vehicle to nose down as the rear part of the vehicle starts to lift this causes the center of mass to move dynamically forward and off-center. It is as though the four-wheeled vehicle has become a three-wheeled vehicle with a center of mass outside the triangular footprint of the three remaining tires. Needless to say the vehicle suspension is operating in a far from optimal condition. Steering inputs become exaggerated causing an oversteer condition to exist. Braking in combination with steering can exacerbate the problem.
The driver in his best attempts to react may simply make matters worse. In the aircraft industry, trained pilots were found to, in attempts to correct for equipment malfunctions, simply make the wrong choices, this is called xe2x80x9cpilot errorxe2x80x9d. Often times what appears to be an appropriate corrective response simply is not in today""s sophisticated aircraft. Similarly xe2x80x9cdriver errorsxe2x80x9d in flat tire situations occur not so much because the driver failed to do something but precisely because he did react and the actions taken made the situation worse. These problems all seem to be greatly exaggerated at higher speeds.
At very high speeds such as NASCAR racing vehicles where speeds reach 200 mph. Each wheel position has an inner tire called a safety shield. A cut outer tire can occur while the driver decelerates to control the vehicle. These trained drivers have vehicles that created downward forces on the tires and racing suspensions designed very stiff and low to better handle these occurrences.
Advances in run flat tires for passenger tires have minimized the occurrence of rapid loss of tire inflation. Nevertheless the wrong reactions of the driver to low pressure in any pneumatic tire or a sudden loss of air pressure is still an issue. Therefore, recent legislation has mandated tire inflation warning systems been installed in vehicles in some countries, the United States being most notable.
The present invention advances that state of the art form a warning to a more integrated vehicle controlled system that compensate for erroneous driver reactions by either overriding the drivers braking input or steering input or by correcting the input to match the vehicles change in responsiveness due to the loss of pressure in the tire. What makes this invention described hereinafter, truly valuable is the initiation on all vehicle response changes are initiated by a change in the tire condition. When one contemplates the fact that the four tire contact patches formed by the tread touching the roadway initiate all vehicle movements, forward, turning, stopping and ride dampening it is absolutely true that transportation is really enabled and controlled by the tires. It is therefore most logical that the fastest most reliable system or components to feedback information to the vehicle should dictated by the tires. The following description shows very useful application of tire initiated vehicle control.
A tire initiated vehicle control system for automobile type vehicles having vehicle components including a power train, a steering mechanisms, a plurality of wheel brake mechanisms, one wheel brake mechanism being at each wheel position, four or more pneumatic tires, a fuel or vehicle throttle with or without a cruise control system and a vehicle suspension system is disclosed.
The vehicle control system has a tire pressure detection device for sensing tire pressure of each pneumatic tire and a control means for receiving data from the pressure detection device. The control means processes the received data and upon a preset pressure or rate of change value in tire pressure the control means directs a change in the response rate of one or more of the following vehicle components; the power train, the steering mechanism, the fuel or vehicle speed throttle, or the vehicle suspension system.
At the onset of a loss of air pressure in any of the pneumatic tires as evidenced by the tire pressure detecting device indicating a preset pressure or rate of change in tire pressure has occurred the control means receives a signal, processes the data and directs a change in response rate of one or more of the vehicle components. The changes can include lowering the vehicle suspension at one or more wheel position, shifting the center of mass of the vehicle directly away from the deflated tire, changing the steering response rate thereby lowering the wheel movement relative to steering input to minimize oversteering, disengaging the cruise control mechanism, having the control means take over the fuel or vehicle speed throttle to regulate vehicle speed, initiating xe2x80x9cbrake steeringxe2x80x9d programs to the brake mechanisms to maintain a controlled vehicle deceleration.
At the time of the flat tire occurrence, the vehicle control system will have initiated changes in one or more of the response rates and thereby will be bringing the vehicle to a controlled speed or to enable the driver to more safely pull the vehicle over for a tire changeover.
In this fashion driver error input can be minimized preventing over braking input or oversteering input. The fact that the pressure detection device can respond in close to real time means the response rate of the control means directing this changes can occur almost, instantaneously. This feature insure that the driver cannot intervene faster that the control means can initiate overriding controls at least in terms of steering and braking inputs. Some systems such as activating a lowering of the suspension or shifting the weight of the suspension or shifting the weight balance of the vehicle may in fact take additional time due to the pneumatic or hydraulic systems used. However it can be appreciated that such actions are when used in combination with the brake, steering and throttle control with or without a cruise control system and a vehicle suspension system as described is capable of achieving vehicle controls far faster than the typical driver will be able to perceive a low pressure or flat tire condition.
It is believed preferable that the control means include a computer or microprocessor having sufficient memory capable of storing preset algorithms that upon known variable such as vehicle speed and vehicle yaw or lateral cornering forces may dictate certain alternative response rate changes of the various vehicle components that are subjected to control input changes.
Ideally the driver should only be aware that the vehicle has initiated a flat tire mode by an audible or visual signal. Preferably all vehicle system such as steering and braking will be controlled such that over braking and oversteering is not an issue regardless of the drivers input. In this fashion, driver error can be compensated for in a more reliable manner.
The added benefit of this vehicle control system is runflat type tires can be employed more easily due in part to weight shifts and suspension adjustments being made at the time of the flat tire occurrence. Maximum vehicle speeds under such conditions can be controlled by the control means. This insures the tires when operated uninflated will not be overheated. Furthermore the control means can advise how many miles the tire was operated in the uninflated condition. This more reliably would enable the tire to be inspected for structural damage upon repair.
The tire pressure detection device may be internal of the tire using a microprocessor chip for sending a signal to the controller as is taught in Patent Publication WO01/19626. Alternatively the tire pressure detection device may be incorporated into the ABS brake mechanisms as is taught in the DWS systems. In such a case the variation in tire response to the brake system can predictably identify a tire operating at a low pressure and can, based on known parameters, predict when a preset pressure condition has occurred.
Definitions
xe2x80x9cAntilock Brakes (ABS)xe2x80x9d means any means for preventing the application of a braking input from the driver causing the tires to stop rotating as the vehicle comes to a rapid stop.
xe2x80x9cBraking Mechanismxe2x80x9d means any mechanical or electrical means for retarding the wheel rotation including but not limited to drum brakes, disk brakes, with or without ABS systems.
xe2x80x9cCruise Controlxe2x80x9d means any system or device that controls throttle input to the power train to maintain the vehicle at a constant rate of velocity.
xe2x80x9cElectronic Suspension Programxe2x80x9d means any computer software program used in conjunction with a vehicle""s suspension or antilock brakes to adjust vehicle ride performance on demand.
xe2x80x9cFuel or Vehicle Speed Throttlexe2x80x9d means the entire system that controls the rate of fuel or power inputted to the power train to increase or decrease vehicle speed including the foot or accelerator pedal associated linkages and supply times for feeding gasoline to the engine""s fuel injection or carburetion devices for gasoline burning engines or the similar counterparts for hybrid engines employing fuel cells, or electric motors.
xe2x80x9cPneumatic tirexe2x80x9d means a laminated mechanical device of generally toroidal shape (usually an open torus) having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire through its tread provides traction and contains the fluid or gaseous matter, usually air that sustains the vehicle load.
xe2x80x9cTire pressure sensor or detection devicexe2x80x9d means any system or device capable of measuring the inflation condition of the tires. The measurement can be done directly by monitoring the tires internal pressure condition as occurring or alternatively it can signal when a rate of change in pressure is observed. The measurement can be indirectly achieved wherein changes in torque at the wheel location is measured or changes in radial tire deflection is measured at known speeds and is sensed by any system such as the Antilock brake System. Whether the measurement is direct or indirect the sensing or detection device simply must send a signal to a control means to advise when a measured or predicted tire pressure condition exist evidencing a flat or low pressure in one or more tires.
xe2x80x9cTraction Controlxe2x80x9d means any system designed to adjust for wheel slippage by controlling the drive axle or braking system to achieve a more controllable tire response to the road surface conditions.